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Fetal Aneuploidy Screening Mastery

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The Nasal Bone (NB)

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Focuses on second-trimester nasal bone evaluation. This module reinforces visualization protocols and discusses the clinical implications of a short or absent nasal bone when detected during a mid-trimester scan.

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Complete this lesson and pass the quiz to earn 10 Karma Points and move one step closer to your Fetal Aneuploidy Screening Mastery Certification.

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1. Who first described the characteristic small nose and flat face in Trisomy 21, and in which year?
John Langdon Down, 1866 Nicolaides, 1990 Keeling, 2002 Benacerraf, 1985
2. On radiographs of Trisomy 21 fetuses, which spectrum of nasal bone findings has been described?
Absent ossification only Hypoplasia or shortness only Absent ossification, hypoplasia, shortness, or agenesis Abnormal calcification and broadening
3. In the Keeling et al. study of Trisomy 21 fetuses between 12–24 weeks, what proportion had nasal bone hypoplasia or agenesis?
28% 45% 61% 79%
4. In which scanning plane must the fetal nasal bone be assessed to ensure accurate evaluation?
Coronal facial plane Mid-sagittal plane Axial oblique plane Transverse nasal plane
5. What is the recommended range for the angle of insonation when imaging the fetal nasal bone?
30–90 degrees 45–135 degrees 60–120 degrees 90–180 degrees
6. What specific sonographic error occurs when the angle of insonation approaches 90 degrees during nasal bone imaging?
The nasal bone appears absent The nasal bone appears bifid Margins become harder to distinguish, producing unnaturally large measurements Shadowing obscures adjacent structures
7. By how much did sensitivity of genetic sonography increase when absent nasal bone was added to existing aneuploidy markers?
From 70% to 80% From 75% to 85% From 83% to 90% From 88% to 95%
8. Why is the nasal bone considered an ideal aneuploidy marker compared to other soft markers?
It is the easiest to image in any plane It has high specificity and a low false-positive rate It is present in all aneuploidies It requires no special technique
9. How does the clinical significance of a SHORT nasal bone differ from an ABSENT nasal bone?
No difference — both carry identical risk Short nasal bone is only significant postnatally Short NB increases risk in high-risk groups; absent NB is a strong marker in all Absent nasal bone is only significant in the first trimester
10. Beyond simple presence or absence, what additional nasal bone assessment in the second trimester offers superior clinical value?
Nasal bone echogenicity grading Nasal bone length measurement Nasal bone angle measurement Nasal tip soft tissue thickness